New Test Distinguishes Zika from Similar Viral Infections

Researchers at UC Berkeley and Humabs BioMed, a private biotechnology company have developed a new test  an antibody-based assay – to differentiate Zika infections from infections from another virus of the same family like dengue and West Nile viruses. This new test is said to be the best till date as it is simple in nature, highly effective, and low-cost too.

Known to cause severe congenital birth defects, Zika is a mosquito-borne disease. There already exist tests that can detect Zika virus infection. But, these tests have some limitations which often renders them useless. Either these tests need to be carried out shortly after infection or they do not fare well in differentiating Zika from other flaviviruses. Because of their limited ability in detecting Zika virus – there have been hindrances to determine the prevalence of Zika virus infections, the cases of congenital Zika syndrome and the frequency of neurological complications associated with Zika virus infections.

The article with results from the study was published online recently in the journal Proceedings of the National Academy of Sciences.

The newly developed assay is very promising with high sensitivity of 91.8 percent and specificity of 95.9 percent for identifying Zika virus infections. The licensing process of the assay is underway and the researchers are hopeful that the test will be available to the medical community soon. The research that led to the assay was funded, in part, by grants from National Institutes of Health.

Eva Harris, study co-author, and UC Berkeley professor in the Division of Infectious Diseases and Vaccinology at the School of Public Health remarked that there was an urgent need for a serological method to differentiate dengue virus from Zika virus infections. This is the first of its kind to have such high sensitivity and specificity in dengue-endemic regions.

The proprietary CellClone discovery technology of the Humabs BioMed lab was applied to generate a new human antibody to the Zika virus, which was then used by the company to develop the assay. The premise of the assay is a well-established approach that is used to detect viral infection. However, what gives this assay the edge over others is the use of new antibody and protocol which further fortifies the two key assay metrics – superior sensitivity and specificity.

As a part of the development process, the assay was implemented in five countries. There it was tested using a large number of clinical samples from travelers and patients living in areas with a high level of exposure to Zika virus and other flaviviruses.

The study data reveals that the new assay was robust with high sensitivity and specificity. When performed on a control group of 540 patients infected with other flavivirus and on patients infected with Zika virus, the specificity of the assay was found to be 95.9 percent.

What played a big role in the development of this assay was the use of detailed patient samples from Harris’s collaborative studies in Nicaragua. Not only the sample included multiple, longitudinal samples from Zika patients, some of which had prior exposure to dengue virus and some not, but also there were samples from dengue patients who were infected once or more with different types of the dengue virus. The variety in the sample was a big plus. The samples were collected over a 14-year study of a cohort of children whose previous viral infection histories were well documented. Since, there is a chance that prior dengue virus infections can cross-react and confound many current Zika antibody-based assays, a thoroughly analyzed pool of patient samples was a key contributor towards the successful development of the assay as it removed the chances of cross-reactivity.

Davide Corti, senior vice president and chief scientific officer of Humabs BioMed remarked that the results of the assay speak for itself. It is highly effective in detecting both recent and past Zika virus infections and it also has the ability to discriminate Zika from other flavivirus infections. He added that they were hopeful that in days to come it will become a simple, effective and low-cost solution for Zika surveillance programs, prevalence studies and clinical intervention trials in flavivirus-endemic areas.

Additional studies are being carried out to further simplify the assay protocol.